Many situations exist in which it is desirable to interrogate fluid samples to determine one or more properties of the fluid, or to gain insight for an evaluation or diagnosis. In particular, the medical industry generates and evaluates numerous fluid samples as a part of ordinary medical care. Certain laboratories currently process about 5,000 of such samples per day, with an expectation that the number of processed samples will double within 4 to 5 years. The sheer volume of samples to be characterized essentially dictates that some sort of automation in sample evaluation is necessary.
A fully automated sample characterization system has several important obstacles to overcome, including ensuring minimum/maximum sample volume and avoiding interferences in the sample and/or incorrect sample content. If the volume of a sample is insufficient, the probe of the analyzer may crash into the bottom of the tube. On the other hand, if the test tube is overfilled, spillage can occur once the cap is removed and the tube is moved around the track system through various robotic systems. Certain fluid samples can contain interferences such as lipemia, icterus, hemolysis, clots, etc. These occurrences may impede the various analyzers and consequently must be accounted for, and sometimes removed from the sample, before the test can be properly completed. Occasionally, a sample labeled as serum actually contains urine and vice versa. In such cases, the sample identification bar codes printed on the tube labels are incorrect, and the samples should be flagged for correction and removed from further processing.
The current state-of-the-art implements prescreening of test tubes for volume, interferences, and/or content, through tedious manual inspection. Each incoming sample is visually inspected for observed interferences. In those cases where labels that are attached to the outside of the tube impede a visual inspection, the technicians will remove the cap and look down into the tube. The need for manual inspection of the tubes can prevent an otherwise automated laboratory facility from increasing sample throughput to a desired daily total. In addition, the frequent need for opening samples exposes technicians to the unknown content of the test tube, may cause contamination of the sample, and may result in spillage from overfilled tubes. Furthermore, visual examination tends to rely on the color of the sample. In certain cases, a technician may not properly identify a sample as urine, which tends to have the same color as blood serum. In addition, the various levels of interferences such as lipemia and hemolysis sometimes produce subtle changes in color, which make visual inspection a significant challenge.
Body fluid samples to be characterized in medical procedures are typically placed into a test tube prior to being delivered to a test facility. Such test tubes are typically made from polypropylene and generally include at least one self-adhering label applied to the side of the tube. The label(s) permit a bar code to be associated with the sample for identification and tracking. Unfortunately, such labels are nonuniform, and present a source of almost random interference for a photometric fluid characterization system. Nonetheless, work has been done to provide photometric fluid characterizing systems that could potentially be modified and adapted to the instant sample verification and screening problem.
In U.S. Pat. No. 5,478,750, the contents of which are incorporated herein by this reference, Bernstein et al. disclose a photometric analyzer for measuring the concentration of substances found in a body fluid sample. This analyzer measures light absorption in the sample at a number of preselected frequencies. Typically, white light is directed through the sample to a pair of apertures that direct light from the sample through a plurality of beam splitters, interference filters, and associated photodetectors. The analyzer further includes means for performing automatic calibration and error checking. They disclose that the effect of random variations between measurements may be minimized by averaging repeated measurements of a given sample. A light wavelength of 850 nm is used as a reference, because while such wavelength is not absorbed by the sample, its intensity is affected to the same degree as the light having relevant characterization wavelengths. The intensity of light at 850 nm and a plurality of detection wavelengths of light passed through a test sample is compared to the corresponding intensity of light at 850 nm and the same plurality of detection wavelengths of light passed through a control sample to determine the degree of light absorption in the test sample due to presence of a known reaction product.
U.S. Pat. No. 6,711,424, the contents of which are incorporated herein by this reference, issued to Fine et al., discloses the use of optical measurement to determine parameter(s) in blood using at least two frequencies of light. The method can be applied to in vivo, and well as in vitro tests. Fine et al. disclose making a plurality of measurements, or continuous measurement spanning a period of time, subsequent to cessation of blood flow. The values obtained from the measurements can be plotted to determine a parametric slope. To determine the parametric slope aimed at determining a desired parameter of blood, at least two wavelengths are selected in accordance with the parameter to be determined. Fine et al. disclose determination of concentration of a substance in a patient's blood by comparing the obtained parametric slope to predetermined calibration curves.
U.S. Pat. No. 6,770,883, the contents of which are incorporated herein by this reference, issued to Mc Neal et al., discloses a method and apparatus for detecting the vertical position of the interfaces between blood cells, plasma, etc., and separation gel in test tubes that may be covered by labels. Their method and apparatus requires shining light having two wavelengths through a test tube to determine an elevation of the interfaces. The first wavelength is transmitted by serum, plasma, labels and the material but substantially blocked by the cells. The second wavelength is substantially blocked by serum, plasma, and cells, but substantially transmitted by the material and labels. The test tube is moved vertically with respect to the light beams, and changes in detected transmission through the tube indicate the location(s) of the interfaces.
U.S. Pat. No. 6,195,158 B1, the contents of which are incorporated herein by this reference, describes an optical scanning system based on an array of LEDs that emit light between 400 and 2500 nm. The length of the array corresponds to the length of the tube such that the entire tube is illuminated. The transmitted light is received on the opposite side of the tube by silicon detectors. By measuring the absorption of different wavelengths and comparing these measurements to values that were obtained through calibration measurements and using statistical analysis, the following parameters can be obtained: height of fluid level, hemoglobin, total bilirubin, and lipids. Also measured is the temperature of the specimen, as well as its type (urine vs. plasma vs. serum).
In United States Patent application No. 2004/0241736, the contents of which are incorporated herein by this reference, Hendee et al. disclose methods and structures adapted to determine one or more attributes in a fluid sample from a spectrum of the sample. Their apparatus includes a light source that can deliver light comprising a plurality of wavelengths to the optical sampling apparatus, a collector that collects light that has interacted with the sample, a spectrometer, and a processor. In general terms, their light source generates infrared light that is directed to the sampling apparatus, where the light interacts with the biological sample. The optical source can optionally comprise a plurality of narrow wavelength devices, such as light-emitting diodes or laser diodes. The exiting light is directed to a spectrometer that yields an absorbance spectrum. The optical measurement system processes the absorbance spectrum using a multivariate calibration model to yield measurements of attributes of the sample, e.g., constituents of a blood sample.
Additional photometric, or optically based, fluid interrogation systems are disclosed in the patent literature. See, e.g., U.S. Pat. Nos. 6,195,158; 6,315,955; 6,628,395; and 6,791,674. Other relevant published United States utility Patent applications may include 2006/0154327. The entire disclosures of all of the aforementioned patents and patent applications are hereby incorporated as though set forth herein, in their entirety, for their disclosures of structure and methods related to radiologically interrogating fluid samples.
To facilitate increased automation of fluid sample testing, and particularly for body fluid sample testing, an improved fully automated system that can prescreen unopened test tubes for sample content and volume is desired. In addition, the prescreening desirably would include the scanning and identification of different anticoagulants such as citrate, EDTA, heparin, or fluoride, which presently cannot be detected through visual inspection, but may have an effect on the sample analysis procedure and/or result.